We detected that paw swelling, AI, alveolitis points, TNFα, and ET-1 expression were significantly increased in rats experimentally developed with adjuvant arthritis, while FVC, FEF25, FEF50, FEF75, MMF, PEF, IL-10, CD4 + Treg, CD4+ CD25+ Treg, and Foxp3 expression in lung tissue were significantly decreased. Here, CD4 is linked to hypersensitivity pneumonitis.